In the heavy industry, large and heavy products can be difficult to handle manually. Thus, a hoist connecting to a clamping device can be used to lift and move heavy objects. An object can be clamped to a clamping device that is coupled to a hoist. The hoist can lift the object to a certain height, and then transfer to a proper location.
The clamping devices can utilize a mechanism that converts the weight of the object into a clamping force, thus the holding force on the object exerted by the clamping devices can be proportional to the weight of the object. A loading and unloading device, such as a crane or a hoist, can be coupled to the clamping device for lifting and transferring the objects.
A basic prior art clamping device can include a rotatable clamping jaw, which can rotate to change a spacing distance to a fixed clamping jaw. Rotation of the rotatable clamping jaw can enlarge or narrow the distance between the two clamp jaws. For example, an object can be placed between the two jaws from a bottom position, and the pushed upward toward the gap between the two jaws. The upward motion of the object can cause a clockwise rotation of the rotatable clamping jaw, which can make the distance between the two jaws larger, to accommodate an object. After the object is placed between the two jaws, the weight of the object can cause the object to move downward. The downward motion of the object can cause a counterclockwise rotation of the rotatable clamping jaw, which can narrow the distance between the two jaws, or to exert a clamping force on the object.
FIGS. 1A and 1B illustrate a prior art clamping device according to some embodiments. The clamping device can include a gripping device normally fabricated from structural steel components, that are designed to securely hold and lift construction materials though a scissor movement. The gripping device can use freely rotating pin connections to create a scissor configuration with two scissor arms.
A first end of the scissor arms is configured to rotate towards each other in reaction to the opposite second end of the scissor arms being lifted vertically. The first end of the scissor arms rotate inwards and generate a compression force clamping on the object to be lifted. Essentially, the weight of the object is used to generate this clamping action.
A clamping device 100 can include two scissor arms 130 and 135, which can freely rotate about a pivot point 130A. The scissor arms 130 and 135 can include upper arms 131 and 136, together with lower arms 132 and 137, respectively, connected at the freely rotating pivot 130A.
The upper arms 131 and 136 can be coupled to pulling elements 111 and 115, respectively. The coupling between the upper arms and the pulling elements can include freely rotating pin connections, e.g., the pulling element 111 and 115 can be rotated relative to the upper arm 131 and 136. The pulling elements 111 and 115 can be coupled to a lift 110, such as a hoist. The coupling between the pulling elements and the lift can include freely rotating pin connections, e.g., the pulling elements 111 and 115 can be rotated relative to the lift 140.
The lower arms 132 and 137 can be coupled to left and right clamps, e.g., holding pads for holding the object, 140 and 145, respectively. The coupling between the lower arms and the holding pads can include freely rotating pin connections, e.g., the holding pads 140 and 145 can be rotated relative to the lower arm 132 and 137.
In operation, an object 120 is placed between the holding pads 140 and 145. The lift 110 is pulled up, which pulls on the pulling elements 111 and 115. The pulling elements 111 and 115 can in turn pull on the upper arms 131 and 136. The scissor movement between the upper arms 131 and 136 and the lower arms 132 and 137 around the pivot point 130A can turn the pulling action on the upper arm 131 and 136 into a pressing action of the lower arm 132 and 137, which presses on the object 120 through the holding pads 140 and 145.
As shown in FIG. 1A, the clamping device 100 operates well to hold the object 120 for lifting and then moving to new location. The weight of the object can be converted to a gripping force from the holding pads for securing the object.
Disadvantages of the clamping devices can include weak handling operations, such as requiring multiple operators for handling. For example, when the empty gripper device is pulled up, the holding pads are pressed together (FIG. 1B). Thus when the empty gripper is lowered to approach the object, another operator might be needed to manually separate the holding pads to place the object between the holding pads.